1. Field of the Invention
This invention relates to a digital camera incorporating a small-sized shutter device unit and a personal digital assistant provided with this digital camera.
2. Description of Related Art
In general, a camera shutter device is previously unified as a component of a camera and is incorporated in a camera body, together with other parts and components, when the camera is fabricated. Because a favorable photographic image cannot be obtained if exposure control is improper, the shutter device is a component that is extremely important for the camera. The shutter device has formerly been fabricated, such that, at completion of fabrication, the shutter device is incorporated to a shutter unit, which is then incorporated into the camera, wherein readjustment of the shutter device is unnecessary.
The shutter device, as is well known, is constructed with numerous parts. In the is fabrication, since each of these parts has an allowable error, individual differences arise among shutter devices at the stage of assembly and some of the shutter devices fail to secure proper control of the amount of exposure within tolerances. Thus, formerly, all shutter devices have been inspected at the stage of assembly and various mechanical and/or electrical adjusting operations have been performed with respect to the shutter devices failing to secure proper control of the amount of exposure. One technique for performing such adjusting operations is set forth in Japanese Patent Kokai No. 2000-47283.
In recent years, however, digital cameras provided with image sensors such as CCDs have become popular, such that extremely small-sized digital cameras are housed in mobile phones and personal digital assistances, called PDAs. In such a digital camera, the photoelectric conversion performance of the image sensor, as well as the shutter device, is a factor which is important for obtaining the proper amount of exposure in photography. Even in the case of the image sensor, however, the allowable error is provided in its fabrication, and thus even when the shutter device is fabricated as mentioned above, the amount of exposure is sometimes not properly controlled at the stage in which the shutter device is incorporated in the camera and is connected to the image sensor for photography. In a conventional digital camera, therefore, after the shutter device and the image sensor are incorporated in the camera body, estimation is made as to whether the proper control of the amount of exposure is carried out so that this amount is adjusted according to the need.
The method of this estimation is that after the shutter device and the image sensor are incorporated in the camera body, the exposure control program of a reference table housed in the camera is used to perform photography under the light source of a is reference amount of light so that estimation is made as to whether the amount of exposure is within a proper range of the reference, and at the same time, so that when it is out of the proper range of the reference, estimation is made as to how large an amount of exposure deviates from the proper range of the reference. In the method of adjusting this amount, it is common practice to use an exposure control program without displacing the shutter device and the image sensor.
In the digital camera, as mentioned above, it is necessary to ascertain whether the amount of exposure can be properly controlled at the stage in which the shutter device and the image sensor are incorporated in the camera body and, if not, to make adjustment so that the amount of exposure can be properly controlled. Conventional digital cameras, therefore, have been designed so that, in order to make such adjustment, an estimation is made as to whether the amount of exposure is within the proper range of the reference, and if not, all of a means of estimating how large an amount of exposure deviates from the proper range of the reference, a plurality of correction means in which the amount of exposure can be corrected in accordance with the deviation amount, and a means of automatically selecting the correction means in accordance with the deviation amount are incorporated in an individual camera. Consequently, there is the problem that an electronic circuit housed in the camera involves a very high cost. Moreover, since electronic parts become bulky and increase in number, a substrate mounted with them also becomes bulky to bring about the problem that this is very disadvantageous for a compact digital camera and a camera housed in the personal digital assistant such as a mobile phone.